A woman died after several members of her ice-fishing party were hospitalized with carbon monoxide poisoning Sunday afternoon in rural Martin County, according to the Martin County Sheriff’s Office.

Police responded to an ice fishing house on Lake Wilmert at 1:55 p.m. and found a 21-year-old woman unresponsive. She died at the scene.

Four other people in the structure were treated for carbon monoxide poisoning, including a 20-year-old man who was transported to Mayo Hospital-Fairmont and then flown to St. Marys Hospital in Rochester.

The cause of the woman’s death is still being investigated by the Ramsey County Medical Examiner’s Office.

From 1999 to 2010, an average of 430 people died unintentionally each year from carbon monoxide poisoning, according to the Centers for Disease Control and Prevention. The death rate was more than three times higher for men than for women.

Martin County is on the Iowa border, between Jackson and Faribault counties.